Various widely used coloured display screens at present, such as a Cathode Ray Tube (CRT) display screen, a light-emitting diode (LED) display screen, an Organic Light Emitting Diode (OLED) display screen, a liquid crystal display (LCD), etc., are all formed by arranging pixels. A coloured display screen includes a plurality of pixels, for example, 640×480, 1024×768, 1920×1080 pixels, and so on. Each pixel includes two or three or more sub-pixels of different colours, wherein, which is more common is that each pixel has three sub-pixels, i.e., a red sub-pixel, a green sub-pixel and a blue sub-pixel. The three sub-pixels are arranged in parallel, to form one pixel.
In order to prevent distortion of an image displayed, each pixel is generally square, and thus, the sub-pixel is rectangular with an aspect ratio of 3:1, as shown in FIG. 1. The plurality of pixels are repeatedly arranged to form the coloured display screen, as shown in FIG. 2. Of course, some of these pixels are self-luminous, for example, an LED coloured display screen, an Active Matrix/Organic Light Emitting Diode (AMOLED) coloured display screen, and so on, and some per se do not emit light, but depend on backlight to supply a light source uniformly, for example, a Passive matrix OLED (PMOLED) coloured display screen and an LCD coloured display screen, and so on.
An important indicator of the coloured display screen is Pixels Per Inch (PPI), that is, a pixel density of the coloured display screen. A major direction of current development of the coloured display screen, is to improve the pixel density of the coloured display screen. A mobile phone screen, a computer screen, and a 4K television of high-resolution in fiery development, etc., put forward higher and higher requirements on the pixel density of the coloured display screen. For example, a Retina coloured display screen produced by the Apple Computer, Inc. has a coloured display screen of high-resolution achieved by reducing a size of each pixel, which has been used in an iphone, a tablet personal computer, a laptop, and so on. The method of directly increasing the pixel density brings two problems difficult to overcome, one is that a fabrication process is complicated, with a low yield, resulting in a high price of the coloured display screen of high-resolution, and the other is that increase in the pixel density means reduction of an area of each pixel, and there is a black gap between the sub-pixels. Therefore, reduction of an area of the sub-pixel renders increase in an area taken by the gap between the sub-pixels, so that a utilization rate of the light source is lowered, and energy consumption of the coloured display screen is remarkably increased in order to achieve a same brightness. This is a fatal weakness for mobile devices such as a mobile phone, a tablet personal computer and a laptop.
In order to reduce the production cost of the coloured display screen and energy consumption in use while improving pixel density, the Samsung Corporation has proposed a variety of new designs and manufacturing methods of the coloured display screen. The corporation improves the pixel density by reducing the number of sub-pixels in each pixel in a Pentile RGBW colour display screen and a Pentile RGBG colour display screen, wherein, the RGBW coloured display screen has sub-pixels of four colours (red, green, blue and white), but each pixel has only two sub-pixels, i.e., blue-white or red-green, with reference to FIG. 3. And in the RGBG coloured display screen, there are ordinary sub-pixels of three colours, but each pixel has only two sub-pixels, i.e., green-blue, or green-red, with reference to FIG. 4. These coloured display screens have the pixel density thereof improved without reducing a size of each sub-pixel. As compared with the Retina coloured display screen of the Apple Inc., it has advantages such as low power consumption and a low cost. Therein, the RGBW coloured display screen has been used in apparatuses below:                Motorola MC65        Motorola ES55        Motorola ES400        Motorola Atrix 4G        Samsung Corporation Galaxy Note 10.1 2014 version        Lenovo Yoga 2 Pro        HP ENVY TouchSmart 14-k022tx Sleekbook        
The RGBG coloured display screen is a very successful coloured display screen of the Samsung Corporation, which has been widely used in a variety of mobile phones, as follows:                BlackBerry Q10        Nexus One        HTC Desire (AMOLED variantsonly)        Samsung Corporation S8000        Samsung Corporation Galaxy S        Samsung Corporation Galaxy S Plus        Samsung Corporation Galaxy S III        Samsung Corporation Galaxy S III Mini        Samsung Corporation Galaxy S 4        Samsung Corporation Galaxy Note        Samsung Corporation Wave S8500        Samsung Corporation Ativ S        Samsung Corporation NX10        Nexus S (Super AMOLED variants only)        Galaxy Nexus        Dell Venue Pro        Nokia N9        Nokia Lumia 800        Nokia Lumia 925        Nokia Lumia 928        Nokia Lumia 1020        HTC One S        Pantech Burst        Huawei Ascend P1        Alcatel One Touch Star 6010D        Motorola RAZR i        
In addition to the above-described method of improving the pixel density by reducing the number of sub-pixels, a variable-structure sub-pixel coloured display screen obtains a higher pixel density and a better display effect by varying a structure of the sub-pixel, for example, an S-Strip coloured display screen of the Samsung Corporation; as shown in FIG. 5, a blue sub-pixel is a long strip, and a red sub-pixel and a green sub-pixel are small squares, which are arranged intersecting with one another to form one pixel. The Samsung coloured display screen technology-related patents are shown in FIG. 6, wherein, a mobile phone Galary S in 2010 and a mobile phone Galary S3 in 2012 use the PenTile RGBG coloured display screen (by the RG pixel and the BG pixel), a mobile phone Galary S2 in 2011 uses a Stripe coloured display screen (the RGB pixel), and a mobile phone Galary Note2 in 2012 uses the S-Stripe coloured display screen (the RGB pixel).
In summary, it can be seen that, at present, a main method for improving the pixel density is to reduce the number of sub-pixels within a single pixel. The method improves the pixel density, while reducing a ratio of a black gap region of a pixel, improving the utilization rate of the light source and reducing the energy consumption for achieving the same brightness. However, as compared with a traditional three-primary colour sub-pixel method, the method reduces quality of the image, so that the displayed image has a certain degree of colour cast.